| 摘要 |
PROBLEM TO BE SOLVED: To suppress an increase in particle concentration in an apparatus and reduce the amount of a settling accelerator additionally added even when the particle size distribution of a component having a true specific gravity smaller than that of the settling accelerator in raw water is so broadened as to include a large particle size.SOLUTION: Raw water contains at least particles having particle sizes distributed in the range of 0.1-1,000 μm and having a true specific gravity of 1.3-1.5 as suspended matter. An inorganic flocculant is added in a first agitation tank, and a polymer flocculant and a settling accelerator are added in a second agitation tank. Then, agitation mixing is carried out. The floc of the suspended matter is formed in a flocculation tank. The floc is settled in a precipitation tank, and the raw water is separated into treated water and slurry. The slurry drawn out from the precipitation tank through a sludge-drawing line is separated into: sludge; and the settling accelerator and the particles. The separated settling accelerator and the particles are fed into the second agitation tank, and the amount of the settling accelerator additionally added and the amount of the slurry discharged from a slurry discharge line which branches off from the sludge-drawing line are controlled so that a slurry density in the sludge-drawing line may become 1,005-1,030 g/L.SELECTED DRAWING: Figure 1 |
